1. Field of the Invention
The present invention relates to polypeptides having xylanase activity and polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.
2. Description of the Related Art
Cellulose is a polymer of the simple sugar glucose linked by beta-1,4 bonds. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
Lignocellulose, the world's largest renewable biomass resource, is composed mainly of lignin, cellulose, and hemicellulose, of which the large part of the latter is xylan. Xylanases (e.g., endo-1,4-beta-xylanase, EC 3.2.1.8) hydrolyze internal β-1,4-xylosidic linkages in xylan to produce smaller molecular weight xylose and xylo-oligomers. Xylans are polysaccharides formed from 1,4-β-glycoside-linked D-xylopyranoses.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the cellulose and hemicelluloase are converted to glucose and xylose, the glucose and xylose can be fermented by yeast into ethanol.
There is a need in the art to improve cellulolytic enzyme compositions through supplementation with additional enzymes to increase efficiency and to provide cost-effective enzyme solutions for degradation of lignocellulose.
The present invention provides polypeptides having xylanase activity and polynucleotides encoding the polypeptides.